Michael Phelps dominated the 2008 Olympics in Beijing, topping Mark Spitz's seven gold medals in one Olympiad with eight of his own. While Phelps isn't one to gloat, those who bet on him are surely doing victory laps.

He's the hero of the Beijing Olympics -- but Michael Phelps has become the bane of bookmakers. Gamblers have joined Phelps's winning streak with online betting sites reporting a spike in money riding on the U.S. swimmer and higher interest overall from gamblers in the Games. Phelps has been the favourite in all of his races in the Aug. 8-24 Games on various online betting sites, with odds for his victories down to about 5/2 on -- paying out about $40 on a $100 bet.